The head of the Ukrainian Catholic Church has called on the people to be ready to sacrifice their lives to protect the country's freedom, as the threat of a Russian attack looms over the horizon.

"Ukraine, unfortunately, has been pulled into a military conflict. So far no one is shooting, so far people are not dying, but it is obvious that military intervention has already begun," Major Archbishop Sviatoslav Shevchuk of Kiev-Halych said in a statement over the weekend, Catholic News Service reported on Monday.

"Our people and our country are currently in danger," the archbishop added. "We must stand up for our country, to be ready -- if necessary -- to sacrifice our lives in order to protect the sovereign, free, independent, and unified state."

The Ukrainian army remained on high alert this week, even though Russian President Vladimir Putin insisted that he was not planning on making Crimea a part of Russia.

Reports noted that 6,000 Russian troops took control of the Crimean Peninsula in Ukraine on Monday, with British Foreign Secretary William Hague calling the crisis the "biggest in Europe in the 21st Century."

While Russia has been blamed by the U.S. and members of the European Union for escalating hostilities in Ukraine, Putin has insisted that former Ukrainian President Viktor Yanukovych is the legitimate leader of the Eastern European country, and that the current interim government is the result of an "anti-constitutional coup and armed seizure of power," CNN reported.

The Russian president also blamed Ukraine's new leaders for destabilizing the southern and eastern parts of the country, but noted that Russians troops so far have not engaged in armed conflict since crossing into Crimea.

Ukraine's interim government has rejected Putin's claims. Andriy Parubiy, head of Ukraine's National Security and Defense Council, meanwhile, announced that the country has doubled its security presence at checkpoints on the borders to prevent incursion by Russian "extremists."

Pope Francis has called on Christians around the world to pray for Ukraine, urging dialogue between the sides involved in the conflict.

"I ask you again to pray for Ukraine, which is in a very delicate situation," the Roman Catholic Church leader said at St. Peter's Square on Sunday.

"While I hope that all sectors of the country will endeavor to overcome misunderstandings and build the future of the nation together, I make a heartfelt appeal to the international community to support every initiative in favor of dialogue and harmony," the pope added.

Archbishop Shevchuk wrote in his pastoral letter for Lent that Ukrainians are entering "the great fast this year with feelings of pain, fear, suffering and trembling hope," and called on Catholics to use the 40 days of Lent "as a time of prayer, fasting and almsgiving to grow closer to God and to one's neighbors."

According to a 2006 poll, Catholics make up only 5.9 percent of Ukraine's population. Eastern Orthodoxy was identified as the biggest denomination in the country, with 26.8 percent of the population affiliated with it.

In February, photos of clergy ministering to people before armed guards and burning barricades emerged in the media. Both Orthodox and Catholic priests stood on the frontlines of clashes between government forces and protesters.